Methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococcus (CoNS) is associated with the presence of the mecA gene (Geha et al., 1994, J. Clin. Microbiol., 32:1768). Isolates of staphylococcus that carry the mecA gene produce a modified penicillin-binding protein, PBP-2′, which confers high-level resistance to all beta-lactams, including penicillins, semisynthetic penicillinase-resistant congeners, penems, carbapenems, and cephalosporins. Isolates of staphylococcus that are mecA positive should be considered resistant to all β-lactam antimicrobials.